Alumina‐toughened zirconia for dental applications: Physicochemical, mechanical, optical, and residual stress characterization after artificial aging

Abstract

To characterize the physicomechanical properties of an alumina-toughened zirconia (ATZ). ATZ synthesis consisted of the addition of alumina particles in an yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) matrix. Specimens were obtained by uniaxial and isostatic pressing ATZ and 3Y-TZP powders and sintering at 1600 C/1 h and 1550 C/1 h, respectively. Crystalline content and residual stress were evaluated using X-ray diffraction (XRD). Microstructure was characterized by scanning electron microscopy (SEM). Optical properties were determined by reflectance test. Mechanical properties were assessed by biaxial flexural strength test. All analyses were performed before and after aging (134 C, 20 h, 2 bar). XRD and SEM revealed a typical ATZ and 3Y-TZP crystalline content, chiefly tetragonal phase, with a dense polycrystalline matrix, though a smaller grain size for ATZ. Aging triggered a similar monoclinic transformation for both systems; however, ATZ exhibited higher residual compressive stresses than 3Y-TZP. While as-processed 3Y-TZP demonstrated significantly higher characteristic strength relative to ATZ, no significant difference was observed after aging ($215 MPa increase in the ATZ strength). ATZ presented significantly higher opacity relative to 3Y-TZP, although aging significantly increased the translucency of both systems (increase difference significantly higher in the 3Y-TZP compared to ATZ). ATZ physicomechanical properties support its applicability in the dental field, with a lower detrimental effect of aging relative to 3Y-TZP.

A novel strategy for fabricating zirconia implants with a trabecular biomimetic porous surface

“…Although pure YSZ is the most common material used in fabricating dental prostheses owing to the high strength, toughness, and translucency, here 90YSZ was explored with an ATZ composite containing 10‐wt.% Al 2 O 3 . Although increasing alumina content would reduce the transformability and the resulting toughness of YSZ, owing to the formation of compressive stresses, the degradation in mechanical properties arising from spontaneous tetragonal‐to‐monoclinic phase transformation in the presence of moisture would also be retarded significantly, increasing the lifetime of components in vivo 26,31 . Moreover, the literature suggests that ATZ composition containing 10–20 wt.% of alumina has the best combination of aging resistance and strength in an aqueous environment for implant applications 26 .…”

“…Although increasing alumina content would reduce the transformability and the resulting toughness of YSZ, owing to the formation of compressive stresses, the degradation in mechanical properties arising from spontaneous tetragonal‐to‐monoclinic phase transformation in the presence of moisture would also be retarded significantly, increasing the lifetime of components in vivo 26,31 . Moreover, the literature suggests that ATZ composition containing 10–20 wt.% of alumina has the best combination of aging resistance and strength in an aqueous environment for implant applications 26 . It is worth noting that the current ceramic dough technique was successfully employed to fabricate components having various ATZ or ZTA compositions along with pure alumina and YSZ as mentioned in our previous work 23 …”

“…26,31 Moreover, the literature suggests that ATZ composition containing 10-20 wt.% of alumina has the best combination of aging resistance and strength in an aqueous environment for implant applications. 26 It is worth noting that the current ceramic dough technique was successfully employed to fabricate components having various ATZ or ZTA compositions along with pure alumina and YSZ as mentioned in our previous work. 23 MicroCT of the implant as shown in Figure 3 also reveals an intact interface between the dense and porous layers.…”

“…Among the alumina-toughened zirconia (ATZ) composites, 90YSZ was chosen for the current study as it has the best combination of strength and aging resistance in an aqueous environment, suitable for dental implant applications. 26 However, for incorporating the trabecular portion over the dense core of the apical region, a gradient structure formation at the interface of densetrabecular portions was explored by employing slurries containing 90YSZ and 50YSZ (50-wt.% Al 2 O 3 + 50-wt.% YSZ). These slurries were prepared using the crushed dried green body of the dough as well as the unused machining dust, in an isopropanol solvent with a powder loading of 0.25-0.45 g/ml depending on the ceramic powder composition.…”

Reaction Sintering of Biocompatible Al2O3–hBN Ceramics

“…BIOLOX Delta is an alumina matrix composite, which combines the excellent tribological behavior of alumina with the good mechanical/toughness properties of yttria-stabilized zirconia . There are however difficulties in controlling phase stability in such materials . Instability results in gradual material strength degradation (so-called aging) caused by the spontaneous transformation of metastable tetragonal ZrO 2 particles into a monoclinic crystalline form. , The transformation manifests itself macroscopically in a 4% volume gain.…”